4

I recently moved emails for domains that I host to gmail (keeping the @mydomain.com email address). I thought I was doing everything right so no emails would be lost, but this turned out not to be the case.

Firstly I set up a google account with email accounts for the email addresses on my domain.

Then I changed the MX records of my domain to gmail's.

I know that propagation of changes takes some time to take affect across the web. I thought that any email sent during this time would either go to the old email accounts or to gmail. I could then use my hosting's IP address to get emails from the old servers, and move them across to gmail's.

However during the switch I sent myself emails as a test and they never appeared in either email account. What's more I also didn't get any error message saying the email couldn't be delivered.

I really need to know what went wrong so in future I can guarantee to my clients that no emails will be lost in the transfer process. An interruption in service is not ideal, but so long as all emails do eventually get delivered then its acceptable.

Evanss
  • 141
  • 1
  • 2

1 Answers1

3

Preface

I'm afraid, here isn't a best place to ask such type of questions: in order to get full detailed answer, we have to cover some deep details of DNS and SMTP. It's a problem for local users here, but not (I hope) on ServerFault

Face

You done almost all correctly, I, maybe, only decreaseвd TTL for MX RR before changing data and would wait data-expiration time in order to make "all perfect"

Main problem is "no any response" from SMTP-transactions in your tests. It's extremely bad sign. Maybe you can check now server-log for MTA, which (first) receive message from your MUA (client program) and must route e-mail message to recipient's server? This way you can at least identify, was message transferred from first hop to next and who to ask for more information about the subsequent history (postmaster@ of collector).

Sorry, without smtp-logs I can't say more

Lazy Badger
  • 3,137
  • 15
  • 13
  • Thank you for your answer. Are you saying that my method should have not resulted in any emails being lost? Thanks –  Feb 12 '12 at 09:55
  • @user793011 - yes, it seems so. You may to get some time e-mails into *both* MX, but not lost - lost mail is a serious reason for special investigation (at least for me, as postmaster with strict professional rules) – Lazy Badger Feb 12 '12 at 10:35
  • My hosting company have said the following: As soon as the MX records are changed, our servers will stop accepting mail for the domain. Some servers may still have the old MX records cached until they expire, though. The expiry time can be reduced by lowering the MX records TTL before making the change, and allowing time for the new TTL to propagate. –  Feb 12 '12 at 12:50
  • And then this: Reducing the TTL before changing the MX records is the best way to avoid losing emails, and the cluster should bounce mail that isn't hosted with us; it just didn't catch up with the change, in this case. Unfortunately, there is no way to absolutely guarantee no email will be lost or bounce during an MX record change from one provider to another. Reducing the TTL before the changeover should minimise the window when that could happen, though. –  Feb 12 '12 at 12:50
  • @user793011 - missing bounces drive me nuts – Lazy Badger Feb 12 '12 at 16:14
  • So is this 'just one of those things' or is my hosing company at fault here? Thanks –  Feb 12 '12 at 20:59
  • *Not* hosting company, definitely. During SMTP-session (shortest: MUA-senderMTA-recipientMTA-MUA) if something go wrong and e-mail can't be transferred, *MTA **must** generate and send bounce-message for sender. Because we don't know now, where and how troubles appeared with undeliverable mail - we don't know to whom really complaint – Lazy Badger Feb 13 '12 at 06:21
  • Is it possible that the test messages all happened to be caught by a spam filter? E.g. they were failed by the SPF due to being sent via the wrong SMTP server (though I don't think Google's SPF is that restrictive)? In some cases, mail server admins choose not to send bounce notifications for messages suspected of being spam. – Lèse majesté Feb 13 '12 at 09:17
  • @Lèsemajesté - yes, it's possible. But in this case message **is received** at least in Google's Spam folder. OP wrote about *"mail disappeared"*. Anyway, currently it's just divination – Lazy Badger Feb 13 '12 at 09:27
  • Well, it depends on where the SPF is enforced. I believe the messages in the spam folder are filtered there post-delivery. Whereas SPF enforcement happens pre-delivery--typically the first MTA to receive the message. Though sometimes the checkpoint won't block the message and will just forward it with a `Received-SPF` header, which Gmail could then use in their spam filter, in which case it _should_ show up in the "spam" folder. But, yea, I guess it's all speculation at this point. – Lèse majesté Feb 13 '12 at 09:43
  • I checked and no messages are in any spam folders. Thanks – Evanss Feb 15 '12 at 18:17